没有看懂这题应该用哪个公式

问题如下：

An analyst gathers the following information:

Which security has the highest beta measure?

选项：

A.

Security 1.

B.

Security 2.

C.

Security 3.

解释：

C is correct.

Security 3 has the highest beta value; $1.07=\frac{\rho_3\sigma_3}{\sigma_m}=\frac{(0.80)(20\%)}{15\%}$ compared to Security 1 and Security 2 with beta values of 1.00 and 0.93, respectively.